The invention relates to a process for biologically treating waste-waters, wherein the waste-water is aerated with pure oxygen and/or air, and in the presence of activated sludge in an activation basin having plural basin sections. The mixture of waste-water and activated-sludge is then removed from the activation basin and is separated, in a finel settling stage, into purified water and sludge. From the final settling stage the sludge is recycled, at least in part, to the activation basin. The invention also relates to an apparatus for implementing the process.
Such a process is disclosed for instance, in German Pat. No. 20 32 480. In this process for treating waste-waters containing biochemically oxidizable ingredients, a gas containing more than 50% by volume of oxygen is passed sequentially through at least two basin sections. Each of the basin sections is sealed in a gas-tight manner with respect to the atmosphere. In order to efficiently utilize the oxygen contained in the gas fed into the basin sections at an economical rate with respect to energy consumption, precautions are taken so that the contents of solids suspended in the liquid in the first basin section will be as high as possible. Furthermore, other precautions are taken to control the liquid supply and the amount of gas fed to the first basin section. Concomitantly, the energy consumption required for the circulation and the mixing in the basin sections is determined as a function of the amount of oxygen contained in the exhaust gas from the last basin section. As a result of the volumes of the individual basin sections being equal, the substrate concentration in the first basin section is often too low for achieving maximum possible consumption of organic materials. Moreover, this occurs even with a high content of suspended solid particles obtained by recycling a corresponding amount of activated sludge. As a result, the most efficient biological performance of the activated sludge is not realized in this type of process.
It is therefore an object of the invention to modify such a process of the initially described type, and to provide equipment for carrying out such a modified process wherein highly efficient biological performance of the activated sludge is achieved in a simple and economical manner.
Upon further study of the specification and appended claims, other objects and advantages of the invention will become apparent.